Field of Invention
The present invention relates to a field of permanent magnetic device, and more particularly to a method for manufacturing a NdFeB rare earth permanent magnetic device with composite plating.
Description of Related Arts
NdFeB rare earth permanent magnetic materials are more and more widely used due to excellent magnetic properties thereof. For example, the NdFeB rare earth permanent magnetic materials are widely used in medical nuclear magnetic resonance imaging, computer hard disk drivers, stereos, cell phones, etc. With the requirements of energy efficiency and low-carbon economy, the NdFeB rare earth permanent magnetic materials are also used in fields such as automobile parts, household appliances, energy conservation and control motors, hybrid cars and wind power.
Conventionally, surface treatment technologies of rare earth permanent magnetic devices are mainly Ni—Cu—Ni electroplating, Zn electroplating, electrophoresis, spraying, etc. Vacuum aluminum plating method is also used. For example, Chinese patent ZL96192129.3 discloses a method of vacuum plating with Ti and AlN; another Chinese patent ZL01111757.5 discloses a method of vacuum evaporation plating with zinc, aluminum, tin and magnesium.
Prior art is shown in FIG. 1, wherein two supporting parts 7 are arranged on an upper portion inside a vacuum chamber 1, and are able to rotate around a shaft 6 along a horizontal axis. Six cylinders 5 made of stainless steel mesh are arranged in a magnetic part 14. Axles 8 are arranged in an external circular direction of the shaft 6 of the supporting part 7 and are supported in a loop form, for rotating around the shaft 6. A plurality of heating boats 2, as evaporating sections of aluminum wires 9 for being evaporated, are arranged on a heating boat supporter 4 extending out from a supporting platform 3 in a lower portion of the vacuum chamber 1. The aluminum wires 9 are mounted and wound around a feeding roller 10 under the supporting platform 3. A front end of the aluminum wire 9 is guided by a heat-resistance protection tube 11 facing an internal surface of the heating boat, for reaching the heating boat. A concave opening 12 is arranged in a section of the heat-resistance protection tube, in such a manner that a gear 13 is mounted corresponding to the concave opening 12 and is directly contacted with the aluminum wire 9. Therefore, by moving the aluminum wire 9 forward, the heating boat 2 is constantly fed, and the aluminum wire 9 is heated for evaporation and deposition on the magnetic part 14 in the rotating cylinder 5 for completing surface aluminum plating.
Conventionally, film plating uses evaporation, resulting in a poor combining force between a film layer and a base, and insufficient improvement of anti-corrosion capacity of the permanent magnetic devices. Magnetron sputtering coating is also conventionally used. Because of low efficiency thereof, magnetron sputtering is unsuitable for low-cost mass production. Some of the prior art have problems of loading, which means loading is not easy and production is difficult. Multi-arc ion plating is also conventionally used. Because of big particles, multi-arc ion plating is not able to reach anti-corrosion requirements of the permanent magnetic device. For overcoming shortcomings of multi-arc ion plating, conventional artisans combine multi-arc ion plating with magnetron sputtering coating, but requirements of high efficiency, low cost and mass production are still not met, and device structure has defects. Especially, conventional rare earth permanent magnetic device electroplating chemical treatment consumes a lot of energy, generates pollution, and requires expensive water treatment equipment, while improper treatment will seriously affect ecological environment. However, according to the present invention, production is provided in vacuum and no pollution material is used, which causes no ecological environment pollution. In the same time, battery effect during electroplating on magnetic performance is lowered. Accordingly, the present invention provides a vacuum composite plating equipment for the rare earth permanent magnetic device, so as to overcome shortcomings of conventional technologies. In addition, NdFeB rare earth permanent magnetic devices produced with the device in the present invention are improved not only in anti-corrosion capacity, bust also in magnetic performance, which significantly improves magnetic energy product and coercivity of the rare earth permanent magnetic devices, saves rare earth resources, and especially saves heavy rare earth which is even rarer.